Image reading device that reads image of document, and image forming device

An image reading device includes a loading plate, a frame, a scanner, a flat cable, and a holding member. The scanner includes a reading mechanism that extends in a main scanning direction and reciprocates in a sub-scanning direction on the side of a bottom surface opposite to an upper surface on which a document on the loading plate in the frame is loaded. The flat cable extends in the frame so that a width direction of the flat surface follows a direction orthogonal to the bottom surface of the loading plate. The holding member reciprocates together with the scanner and holds a part of the flat cable from the side on a main surface of the frame.